Large enterprises often tie geographically remote sites to central computers. As an example, a banking enterprise may provide communication between a central data center that holds bank customer records and each of potentially thousands of branch banks.
To improve communication reliability and load balancing, “multi-homing” may be used in which more than a single communication link can connect network components. Various technologies, sometimes referred to collectively as “optimal exit link selection”, can be used in selecting which particular link is used at a given time, with the decision being reflected in the selection of an “exit link” typically at a border router in the network. The goals may be, e.g., to improve network performance, optimize load distribution, and lower costs for Internet connections.
Link selection can be determined by the results of measuring link performance through probing. Passive probing may be used, in which a network component in essence passively monitors performance by, e.g., detecting whether expected acknowledgement packets are received for transmission control protocol (TCP) traffic, or active probing may be used, in which a network component such as a border router transmits a test signal to a predetermined receiver to monitor the characteristics of the return traffic (e.g., delay, loss, jitter, etc.). Passive probing may be appropriate only for certain types of traffic and may require particular circumstances to function adequately, while active probing consumes network resources requiring, as it does, additional probe test signals to be processed by various components.